- There should be an interval of at least 4 weeks from any previous intensive chemotherapy before beginning flavopiridol, with the exceptions non-aplasia producing treatments (i.e. hydroxyurea, interferon, imatinib, 6MP, thalidomide); patients should have recovered completely from any treatment-related toxicities; patients may have received hematopoietic growth factors previously, but must be off all growth factors (including EPO, G-CSF, GM-CSF, IL-3, IL-11) for at least 4 days prior to beginning flavopiridol